High-frequency translating circuits



Aug. 17 1926.

i 1,596,102 W. H. T. HOLDEN HIGH FREQUENCY TRANSLATING CIRCUITS FiledDec. 24. 1924 INVENTOR WEZ'Ioldew &

ATTORNEY I Patented Aug. 17 1926.

UNITED STATES PATENT" OFFICE.

WILLIAM H. '.I.. HOLDEN, OF BROOKLYN, NEW YORK, ASBIGKOB 'IQ AURIGA]TEL]- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

menrraneunuc rmusnarme cmcurrs.

Application filed December 24, 1924. Serial No. 757,880.

This invention relates to high frequency translating systems andparticularly to a balanced oscillator-modulator or demodulatorcharacterized by the use of Inulti-grid unipotential cathode vacuumtubes, and suppression of the carrier frequency. v

Balanced oscillators and modulators or .demodulators have been designedand used in the radio and carrier art but in all of the arrangements ofthe prior art threeelectrode tubes have been employed. In these circuitsof the prior art the same input and output circuit must perform not onlythe function of creating oscillations but also the function ofmodulating the oscillations as thus created by other oscillations. Sincethe same circuits are employed for different functions it isimpracticable to make the impedanceof these circuits of such value as tobe eificient for one function with ut tending to render theminefiicientto carry out the other function. Accordingly, with circuitsof the prior art'it is necessary to adopt a "value of impedance that'Will give fair results in carrying out both functions. In my copendingapplication, Serial No. 7 57 ,017

filed December 19, 1924, I have dc scribed a multi-grid unipotentialcathode tube and have shown the method of using a tube of that type inan amplifying circuit whereby different degrees of amplification may beproduced. I have found that by using a tube of the type thereindescribed in a balanced oscillator-modulator or demodulator circuit itis practicable to attain hi gh eificiency for eachof the functionsproduced by the device.

T his invention resides in a balanced translating device of highefiiciency capable of producing. oscillations and of modulatm'g ordemodulating other oscillations by those created therein.

This invention will vbe apparent from the following description, read inconnection with-the attached drawing, showing schematically a form ofthe invention.

In the drawing, the input circuit 1 is coupled with the translatingcircuit by means of thetransformer 2. This input circuit is designed toimpress upon the translating circuit either frequencies intended tomodulate the" oscillations generated by the translating circuit orfrequencies intended to be demodulated by beating with the oscillationscreated by the translating circuit.

The translating circuit includes two multigrid unipotential cathodevacuum tubes 3 tube 4. The midpoint of'this winding is connected withthe cathodes 5 and 6, the connection including the winding 10 of thecoupling transformer 11 and the negative biasing battery 12. In likemanner, each of the plates 13 and 14 of the tubes 3 and 4 is connectedthrough one half of the primary winding of the transformer 15 with bothof the cathodes, the connection including the source of plate potential16. The secondary winding of the transformer 15 is connected with theoutput circuit 17. The grids 18 and 19 are connected together with thepositive pole of the source 16 of plate potential, the connectionincluding the tuned circuit made up of the inductance of the winding 20and the capacitance ofthe condenser 21. It should be noted that thepositive potential of the source 16'is connected not only to the plates13 and 14 but also through the conductor 22 and the tuned circuit 2021with the grids 18 and 19. This is important to bear in mind becauseithelps to understand the subsequent. action of the tube. A by-pmcondenser 23 for high frequency currents is connected from conductor 22with the negative side of the biasing battery 12.

The energization of the heating elements associated with the cathodes ofthe tubes cathode of the tube 3 and from the grid 19 to the cathode 6 ofthe tube 4. As in balanced circuits employing three-electrode tubes,each tube of the four-electrode type 5 has an input circuit which may beconsidered as extendin from the cathode to the grid of each tu e, eachcircuit including one-half of an input impedance-which in ordinarypractice in half of a secondary 1o windin of the input transformer. Smoethe cathodes are strapped together and are connected with the midpointof this secondary winding, the negative biasm battery is inserted inthis common con uctor, 1B as also is one of the windings of the couplingtransformer by means of which the feeding back of the oscillations iseffected when the translating clrcuit functions as an oscillator. Thereare two output c1r l0 cuits, one of which functions in the generation ofoscillations, and the other of WhlCh functions in the modulation anddemodulation of oscillations. The output circuit of the generator may beconsidered as extending from the positive pole of the source of platepotential 16 over conducton 22, through the resonant circuit made up ofthe winding 20 and the condenser 21, to the grids 18 and 19, thence tothe cathodes 5 80 and 6 respectively, to the negative pole of the source16. This circuit is coupled with,

' the input circuit through thetransformer- 11. The grids 18 and 19having positive potential applied thereto by the source 16 85 willproduce electron flow through the tubes between the said grids and'theircathodes, which flow will produce a current through the winding 20,which in turn will cause a variation of the current through the 40winding 10, thereby varying the charge-upon the grids 8 and 9. Thisaction is, .of course, the same as in generators of the prior art. Theseoscillations, which are fed back to the input circuit, will combine withthe oscillations impressed upon the input circuit 'by the circuit 1,which'oscillations would probably be of different frequency, as inheterodyning. The oscillations of the two frequencies would then beimpressed upon the grids 5 and 6, thus producing variations in the spacecurrentbetween the plates 13 and 14 and the cathodes 5 and 6respectively, which variations would. be manifested in the outputcircuit 17 as a 66 current the frequency of which would be dependentupon the frequencies beaten together within the modulating device. Theability to employ separate out ut circuits for the oscillating and thedemo ulating (or 00 modulating) function, which is rendered practicableby having separate anodes in each tube, rendersit possible to operatethe tube so as to obtain the maximum efliciency as an oscillator and asa'modulator or demodulator-"by virtue of the fact that the impedance ofeach output circuit may be fixed at whatever value is necessary in orderto produce the maximum efficiency of the translating circuit for'eachfunction.

A further advantage of the circuit shown arises from the use ofunipotential cathode tubes which renders it practicable to employ asource of alternating current as, for example, a house lighting system,to render the cathodes electron-emitting.

While this invention has been disclosed as embodied in a particular formit is ca able of embodiment in other and different orms withoutdeparting from the spirit, and scope of the appended claims.

What is claimed is:

1. In an oscillating-modulating device the combination with'a pair oftubes each having an electron-emitting cathode, a plate, a main grid andan auxiliary grid, an input impedance having each terminal connectedwith the main grid of each tube and having its midpoint connected withthe cathode: of both tubes, the connection including a negative biasingbattery and one winding of a feed-back transformer, an output impedancehaving each terminal connected with the plate of each tube, a source ofpotential having its negative pole connected with both cathodes andhaving its positive pole con. nected with the midpoint of said outputimpedance and with the auxiliary grid of each tube, the latterconnection including a resonant circuit comprising another winding ofthe feed-back transformer shunted by a condenser, the said resonantcircuit being tuned to thedesired beating frequency.

2. In a balanced translating circuit the combination with an inputcircuit of an output circuit, a balanced translating circuit, atransformer connecting the sand input circuit with the said translatingcircuit, a second transformer connecting the output circuit with thesaid translating circuit, the said. translating circuit containing twotubes each having a cathode, means to heat the said cathode, an anode, amain grid and an auxiliary grid, a source of direct current potentialhaving its positive pole connected with the anode of each tube and alsowith the auxiliary grid of each tube, a negative biasing batteryconnected between both cathodes and the 'main grid of each tube, and acoupling transformer having one winding connected between the saidsource of direct current potential and the said auxiliary grid and theother winding connected between the said negative biasing battery andthe said main grid.

3. In an oscillating-modulating device, the combination with a plurality.of vacuum tubes each having a unipotential cathode, a plate, a maingrid, an auxiliary grid, and means to render the said cathodeelectronemitting, an input circuit for each tube, a no negative biasingbattery common to both tential and the said auxiliary grid and the inputcircuits, an output circuit for each other winding connected in thecommon contube, a source of plate potential connected ductor of theinput circuits of the said tubes. 10

with the plates of each tube and also with In testimony whereof, I havesigned my 3 the auxiliary grids of each tube, and a feedname to thisspecification this 23rd day of back transformer having one winding con-December, 1924. nected between the said source of plate po WILLIAM H. T.HOLDEN.

